<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:80c0e6a1-a57d-43f6-a3cc-2db40c4ba81e,g:d2480bdc-1b9b-435c-a693-0afb8d798528-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="drs-20250930.xsd#ConsolidatedStatementsofCashFlowsUnaudited"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/ConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5fde16b9-c927-4577-9728-307662ed641e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_StatementTable_5fde16b9-c927-4577-9728-307662ed641e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_571451e0-88f0-4208-a5fe-5434372d6c9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5fde16b9-c927-4577-9728-307662ed641e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_571451e0-88f0-4208-a5fe-5434372d6c9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_571451e0-88f0-4208-a5fe-5434372d6c9a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_571451e0-88f0-4208-a5fe-5434372d6c9a" xlink:to="loc_us-gaap_RelatedPartyDomain_571451e0-88f0-4208-a5fe-5434372d6c9a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_ac2866e2-3c56-4172-bbe6-ac5f5baaf444" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_571451e0-88f0-4208-a5fe-5434372d6c9a" xlink:to="loc_us-gaap_RelatedPartyDomain_ac2866e2-3c56-4172-bbe6-ac5f5baaf444" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_6be826d0-b045-4de3-84c8-ecfdfc3f4b27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_ac2866e2-3c56-4172-bbe6-ac5f5baaf444" xlink:to="loc_us-gaap_NonrelatedPartyMember_6be826d0-b045-4de3-84c8-ecfdfc3f4b27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_82751683-d19f-43fc-9ecb-03c92c472617" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_ac2866e2-3c56-4172-bbe6-ac5f5baaf444" xlink:to="loc_us-gaap_RelatedPartyMember_82751683-d19f-43fc-9ecb-03c92c472617" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_36eec392-0cf0-4fd5-81bb-2693d756747d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_36eec392-0cf0-4fd5-81bb-2693d756747d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_6fc2f80e-4ac8-4ba9-b1f1-fab9c53506f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_36eec392-0cf0-4fd5-81bb-2693d756747d" xlink:to="loc_us-gaap_NetIncomeLoss_6fc2f80e-4ac8-4ba9-b1f1-fab9c53506f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_36eec392-0cf0-4fd5-81bb-2693d756747d" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_8170bbb4-1ba0-4eec-ae6d-e561f48b053d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_8170bbb4-1ba0-4eec-ae6d-e561f48b053d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_5c58d9b5-c3ee-4ca1-a45b-2da8f95071a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_5c58d9b5-c3ee-4ca1-a45b-2da8f95071a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_da0d1c94-b811-4d8b-828c-3ee42fc83921" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:to="loc_us-gaap_ShareBasedCompensation_da0d1c94-b811-4d8b-828c-3ee42fc83921" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_3db7bde7-00c5-4b69-be06-ec40df9750d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherOperatingActivitiesCashFlowStatement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:to="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_3db7bde7-00c5-4b69-be06-ec40df9750d4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_31ddc469-a408-4192-a7df-c96c5a04eff5" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_cf30928b-60a5-407c-9717-4cfc828b7d81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_cf30928b-60a5-407c-9717-4cfc828b7d81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_02bd2527-bdfc-45af-b0aa-c5019e41c619" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_02bd2527-bdfc-45af-b0aa-c5019e41c619" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_f530ecb7-84e6-4328-9a92-758bb1a479a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_f530ecb7-84e6-4328-9a92-758bb1a479a0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_78033a11-73d9-4b15-bef6-5add3ae45f0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPrepaidExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidExpense_78033a11-73d9-4b15-bef6-5add3ae45f0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_2e301d34-6298-4bad-97ff-5919f8c5b3de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_2e301d34-6298-4bad-97ff-5919f8c5b3de" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_08f275e3-e43f-454b-8e16-121a4b7a16de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_08f275e3-e43f-454b-8e16-121a4b7a16de" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_2d91ee7b-40cc-4619-80db-841edea6fb9c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInPensionAndPostretirementObligations_2d91ee7b-40cc-4619-80db-841edea6fb9c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_5cc41583-1fca-40ff-a42f-b1fa27aa1d10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_5cc41583-1fca-40ff-a42f-b1fa27aa1d10" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_d5320d60-6465-4e91-a8f0-9baae42320fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_d5320d60-6465-4e91-a8f0-9baae42320fe" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_079a3b6f-5489-4d9e-b259-5504ce484e7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_079a3b6f-5489-4d9e-b259-5504ce484e7d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_d84ac3c8-9076-47e3-a70a-6f4c1af9b3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_db390e1e-4b94-40ed-8dae-ebe36e610086" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_d84ac3c8-9076-47e3-a70a-6f4c1af9b3a1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_6b697526-0c78-40fc-88f7-f677948cc66c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_36eec392-0cf0-4fd5-81bb-2693d756747d" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_6b697526-0c78-40fc-88f7-f677948cc66c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_13a6b1a3-f03f-4881-9110-3b1b89c269dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_13a6b1a3-f03f-4881-9110-3b1b89c269dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_c50edb54-f438-4f2f-b7d8-cb888da94e7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:to="loc_us-gaap_ProceedsFromSaleOfProductiveAssets_c50edb54-f438-4f2f-b7d8-cb888da94e7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromInvestments_4e56db76-eaeb-477e-960c-cc5954c6e14e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForProceedsFromInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:to="loc_us-gaap_PaymentsForProceedsFromInvestments_4e56db76-eaeb-477e-960c-cc5954c6e14e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_b936b927-afbd-431b-ad62-bbd4df30d8e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_0f1f6aad-1bf9-4e58-9217-443c693ffa6a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_b936b927-afbd-431b-ad62-bbd4df30d8e2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess_83f30c1f-fb7e-4b4e-8c9b-a1e244cfb9c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess_83f30c1f-fb7e-4b4e-8c9b-a1e244cfb9c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_f131bf93-ebf9-4c17-a6cf-220531c478a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_f131bf93-ebf9-4c17-a6cf-220531c478a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_4673f4ba-be22-40e7-aeb8-f2376eb9007d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_4673f4ba-be22-40e7-aeb8-f2376eb9007d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_13ea3ccc-9095-4fd1-986c-5a56905a2a2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_13ea3ccc-9095-4fd1-986c-5a56905a2a2f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_6c0b2d67-c3b1-4fd4-a575-72c33137314c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_6c0b2d67-c3b1-4fd4-a575-72c33137314c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_55b77a0f-3f96-44a5-a820-88efb9e8baa4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_55b77a0f-3f96-44a5-a820-88efb9e8baa4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_e5308f75-888a-4ccf-a774-64d841712a4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_PaymentsOfDividends_e5308f75-888a-4ccf-a774-64d841712a4a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_78fa3e70-9901-4dd6-84e1-2aa78fecd87a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividends"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_37808c7b-7972-4f2d-a77b-77659cd8df58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_37808c7b-7972-4f2d-a77b-77659cd8df58" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_e03bcefe-a3e6-48ee-9ec0-e4b119a17261" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_2abebbe5-78a7-4efc-8e4e-d6f3c839a9e4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_e03bcefe-a3e6-48ee-9ec0-e4b119a17261" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_ab9b789d-3986-49b2-bb42-335b211ee565" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_ab9b789d-3986-49b2-bb42-335b211ee565" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_a5a8e931-b550-4374-9341-c2d3fc660e85" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_a5a8e931-b550-4374-9341-c2d3fc660e85" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_a200fee5-f756-4a1e-939c-9961f1bab6da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7e08669d-f631-4265-aae3-e78fef52cb46" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_a200fee5-f756-4a1e-939c-9961f1bab6da" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_75eeb625-b529-448d-ab55-80af3baab270" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/ConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="simple" xlink:href="drs-20250930.xsd#ConsolidatedStatementsofShareholdersEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/ConsolidatedStatementsofShareholdersEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b6d32aa2-4fee-49a1-9f8a-f8d0b31bbbc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_29bb8d46-f16c-41fd-8815-3d51b52e15cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b6d32aa2-4fee-49a1-9f8a-f8d0b31bbbc1" xlink:to="loc_us-gaap_StatementTable_29bb8d46-f16c-41fd-8815-3d51b52e15cb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_a156a8f5-3c6b-45c6-8563-21a76e9f2546" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_29bb8d46-f16c-41fd-8815-3d51b52e15cb" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_a156a8f5-3c6b-45c6-8563-21a76e9f2546" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a156a8f5-3c6b-45c6-8563-21a76e9f2546_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a156a8f5-3c6b-45c6-8563-21a76e9f2546" xlink:to="loc_us-gaap_EquityComponentDomain_a156a8f5-3c6b-45c6-8563-21a76e9f2546_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a156a8f5-3c6b-45c6-8563-21a76e9f2546" xlink:to="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_16ffc0c9-1336-4cc4-b448-8ba377ef4dd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:to="loc_us-gaap_CommonStockMember_16ffc0c9-1336-4cc4-b448-8ba377ef4dd4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_adb0f7d6-afb3-4079-be6a-c0042b7d2f26" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_adb0f7d6-afb3-4079-be6a-c0042b7d2f26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b873bc3d-2978-4470-adfc-98a2ccc80566" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_b873bc3d-2978-4470-adfc-98a2ccc80566" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_f67410bf-736f-4ce0-9701-a5df3e96b8b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_fe3c2593-c8a2-4ed0-9a65-71263348e9ba" xlink:to="loc_us-gaap_RetainedEarningsMember_f67410bf-736f-4ce0-9701-a5df3e96b8b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b6d32aa2-4fee-49a1-9f8a-f8d0b31bbbc1" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_8bed69a9-1a38-45dc-83ca-cc0303a6170f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_StockholdersEquity_8bed69a9-1a38-45dc-83ca-cc0303a6170f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_0b081b60-c702-4139-83b0-02fa57a280c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_0b081b60-c702-4139-83b0-02fa57a280c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_0342cc80-f1d6-4478-978e-68555c45deeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_0342cc80-f1d6-4478-978e-68555c45deeb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_5b9f85dc-5719-4721-bc94-701d4b864ef3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_5b9f85dc-5719-4721-bc94-701d4b864ef3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings_43da896e-0cfe-4fb1-bfb6-dd996286f827" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings_43da896e-0cfe-4fb1-bfb6-dd996286f827" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_0e45facd-ae91-4ab0-8b0f-f0b69ef599c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_beeabe40-d8d0-416c-95e6-824508ebd916" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_0e45facd-ae91-4ab0-8b0f-f0b69ef599c9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_0588bf80-c15f-40e8-84a7-cb9edad417df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#SummaryofSignificantAccountingPoliciesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SummaryofSignificantAccountingPoliciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_57bc307d-bf5e-407b-967c-784ba9915f78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_17010e8b-e682-411d-ad63-392a3bbf8167" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_57bc307d-bf5e-407b-967c-784ba9915f78" xlink:to="loc_us-gaap_ConcentrationRiskTable_17010e8b-e682-411d-ad63-392a3bbf8167" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_07a38718-7c8a-45b2-a6d4-97fc9fe7732d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_17010e8b-e682-411d-ad63-392a3bbf8167" xlink:to="loc_srt_MajorCustomersAxis_07a38718-7c8a-45b2-a6d4-97fc9fe7732d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_07a38718-7c8a-45b2-a6d4-97fc9fe7732d_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_07a38718-7c8a-45b2-a6d4-97fc9fe7732d" xlink:to="loc_srt_NameOfMajorCustomerDomain_07a38718-7c8a-45b2-a6d4-97fc9fe7732d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_fc24db11-eed1-4ac8-b191-b6f617c8c609" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_07a38718-7c8a-45b2-a6d4-97fc9fe7732d" xlink:to="loc_srt_NameOfMajorCustomerDomain_fc24db11-eed1-4ac8-b191-b6f617c8c609" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_USDepartmentOfDefenseMember_9f8299f9-01f8-4b99-8f6d-348dc0ff0060" xlink:href="drs-20250930.xsd#drs_USDepartmentOfDefenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_fc24db11-eed1-4ac8-b191-b6f617c8c609" xlink:to="loc_drs_USDepartmentOfDefenseMember_9f8299f9-01f8-4b99-8f6d-348dc0ff0060" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_InternationalAndCommercialCustomersMember_6dd2bffc-e31f-4643-9e61-af1e9a585bd5" xlink:href="drs-20250930.xsd#drs_InternationalAndCommercialCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_fc24db11-eed1-4ac8-b191-b6f617c8c609" xlink:to="loc_drs_InternationalAndCommercialCustomersMember_6dd2bffc-e31f-4643-9e61-af1e9a585bd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_6e7909c2-f381-4008-a5d5-e1621a495dbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_17010e8b-e682-411d-ad63-392a3bbf8167" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_6e7909c2-f381-4008-a5d5-e1621a495dbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_6e7909c2-f381-4008-a5d5-e1621a495dbf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_6e7909c2-f381-4008-a5d5-e1621a495dbf" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_6e7909c2-f381-4008-a5d5-e1621a495dbf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_02318267-6c56-4b57-85aa-173563c69110" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_6e7909c2-f381-4008-a5d5-e1621a495dbf" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_02318267-6c56-4b57-85aa-173563c69110" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_838899bc-866c-41a3-8831-5d8a30cb93e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_02318267-6c56-4b57-85aa-173563c69110" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_838899bc-866c-41a3-8831-5d8a30cb93e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_f6eaceb9-b521-438c-adfc-baf47e064220" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_17010e8b-e682-411d-ad63-392a3bbf8167" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_f6eaceb9-b521-438c-adfc-baf47e064220" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_f6eaceb9-b521-438c-adfc-baf47e064220_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f6eaceb9-b521-438c-adfc-baf47e064220" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_f6eaceb9-b521-438c-adfc-baf47e064220_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_2552b7b1-a862-45c9-858b-096e8c6e3c02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_f6eaceb9-b521-438c-adfc-baf47e064220" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_2552b7b1-a862-45c9-858b-096e8c6e3c02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GovernmentContractsConcentrationRiskMember_6e6c6d38-36fa-436f-952f-e869d64f7a73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GovernmentContractsConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_2552b7b1-a862-45c9-858b-096e8c6e3c02" xlink:to="loc_us-gaap_GovernmentContractsConcentrationRiskMember_6e6c6d38-36fa-436f-952f-e869d64f7a73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_af095cc5-5a65-48a5-940d-446d8d79e911" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_2552b7b1-a862-45c9-858b-096e8c6e3c02" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_af095cc5-5a65-48a5-940d-446d8d79e911" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_6f909ecc-d56b-46d1-aca3-bf7c771118e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_57bc307d-bf5e-407b-967c-784ba9915f78" xlink:to="loc_us-gaap_NumberOfReportableSegments_6f909ecc-d56b-46d1-aca3-bf7c771118e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_1b58fd5a-edb3-44ed-b88b-a327db718ea0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_57bc307d-bf5e-407b-967c-784ba9915f78" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_1b58fd5a-edb3-44ed-b88b-a327db718ea0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersEstimateatCompletionAdjustmentsDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#RevenuefromContractswithCustomersEstimateatCompletionAdjustmentsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersEstimateatCompletionAdjustmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInAccountingEstimateLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_9cdcaff4-ed94-4735-88a0-287296baee23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfChangeInAccountingEstimateTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:to="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_9cdcaff4-ed94-4735-88a0-287296baee23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ac93c416-4b51-4f3e-8390-3c6e9a79ceba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInAccountingEstimateByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfChangeInAccountingEstimateTable_9cdcaff4-ed94-4735-88a0-287296baee23" xlink:to="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ac93c416-4b51-4f3e-8390-3c6e9a79ceba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_ac93c416-4b51-4f3e-8390-3c6e9a79ceba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ac93c416-4b51-4f3e-8390-3c6e9a79ceba" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_ac93c416-4b51-4f3e-8390-3c6e9a79ceba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_0a9075bf-c774-410b-a1ca-877860e06605" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ChangeInAccountingEstimateTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ChangeInAccountingEstimateByTypeAxis_ac93c416-4b51-4f3e-8390-3c6e9a79ceba" xlink:to="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_0a9075bf-c774-410b-a1ca-877860e06605" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember_5a21e661-5be2-4eb4-bca3-355bd8531f27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateTypeDomain_0a9075bf-c774-410b-a1ca-877860e06605" xlink:to="loc_us-gaap_ContractsAccountedForUnderPercentageOfCompletionMember_5a21e661-5be2-4eb4-bca3-355bd8531f27" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_RevenueAndOperatingIncomeLoss_2d03209e-299f-4416-a17e-b4e449009010" xlink:href="drs-20250930.xsd#drs_RevenueAndOperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:to="loc_drs_RevenueAndOperatingIncomeLoss_2d03209e-299f-4416-a17e-b4e449009010" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent_829974f2-4f27-47ad-bfbd-0bfcbb87ecc2" xlink:href="drs-20250930.xsd#drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:to="loc_drs_RevenueFromContractWithCustomerExcludingAssessedTaxPercent_829974f2-4f27-47ad-bfbd-0bfcbb87ecc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_7d157381-c8f2-46d6-8c41-c665cded3177" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:to="loc_us-gaap_NetIncomeLoss_7d157381-c8f2-46d6-8c41-c665cded3177" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_55276ebc-88ce-499d-be97-2d2472c3611c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ChangeInAccountingEstimateLineItems_2d3bb40a-3d48-476f-8644-e77563dbe1b5" xlink:to="loc_us-gaap_EarningsPerShareDiluted_55276ebc-88ce-499d-be97-2d2472c3611c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_a2a45a49-54ee-4dfa-ae6f-57b12d4df131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_a2a45a49-54ee-4dfa-ae6f-57b12d4df131" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:to="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d8ca1ea5-5784-48f1-a4f6-d53346b37caa_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:to="loc_srt_ProductsAndServicesDomain_d8ca1ea5-5784-48f1-a4f6-d53346b37caa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:to="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_9c944d2a-5b20-466d-9589-395ba8e78f1b" xlink:href="drs-20250930.xsd#drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:to="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_9c944d2a-5b20-466d-9589-395ba8e78f1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_4315549b-1928-4295-9d0b-3314e4a17eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_4315549b-1928-4295-9d0b-3314e4a17eaf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_377736cf-e658-4fb4-a8a5-5cddd1c9d300" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_377736cf-e658-4fb4-a8a5-5cddd1c9d300" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_99942858-fc91-4029-a849-0a172e9c9cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_99942858-fc91-4029-a849-0a172e9c9cb8" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1" xlink:type="simple" xlink:href="drs-20250930.xsd#RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersRemainingPerformanceObligationsNarrativeDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_05bfba84-700c-4ba7-a85a-ab64886dd907" xlink:to="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d8ca1ea5-5784-48f1-a4f6-d53346b37caa_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:to="loc_srt_ProductsAndServicesDomain_d8ca1ea5-5784-48f1-a4f6-d53346b37caa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_d8ca1ea5-5784-48f1-a4f6-d53346b37caa" xlink:to="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_9c944d2a-5b20-466d-9589-395ba8e78f1b" xlink:href="drs-20250930.xsd#drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_c7b0bf66-cca2-4574-9342-ebde29251349" xlink:to="loc_drs_LongTermContractsOnElectricPowerAndPropulsionProgramsMember_9c944d2a-5b20-466d-9589-395ba8e78f1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_4315549b-1928-4295-9d0b-3314e4a17eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_4315549b-1928-4295-9d0b-3314e4a17eaf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_377736cf-e658-4fb4-a8a5-5cddd1c9d300" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_377736cf-e658-4fb4-a8a5-5cddd1c9d300" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_99942858-fc91-4029-a849-0a172e9c9cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_5fe2a8ab-6e2d-451f-94ad-8756e5ca41af" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_99942858-fc91-4029-a849-0a172e9c9cb8" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#RevenuefromContractswithCustomersDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RevenuefromContractswithCustomersDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_adfc54fe-1cc4-4c6b-8624-2818debe7d1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_adfc54fe-1cc4-4c6b-8624-2818debe7d1a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_821e7d50-99eb-4acb-8010-f16c293dce5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_821e7d50-99eb-4acb-8010-f16c293dce5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_821e7d50-99eb-4acb-8010-f16c293dce5a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_821e7d50-99eb-4acb-8010-f16c293dce5a" xlink:to="loc_us-gaap_SegmentDomain_821e7d50-99eb-4acb-8010-f16c293dce5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_31fa3678-e101-4cdf-b48f-fd863fffc07a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_821e7d50-99eb-4acb-8010-f16c293dce5a" xlink:to="loc_us-gaap_SegmentDomain_31fa3678-e101-4cdf-b48f-fd863fffc07a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_000ab0f9-50d1-42b4-8d3d-eadeabdd3cb8" xlink:href="drs-20250930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_31fa3678-e101-4cdf-b48f-fd863fffc07a" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_000ab0f9-50d1-42b4-8d3d-eadeabdd3cb8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_a595a440-0277-4166-a029-b6649d522143" xlink:href="drs-20250930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_31fa3678-e101-4cdf-b48f-fd863fffc07a" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_a595a440-0277-4166-a029-b6649d522143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_6cdb9778-bbc0-4c00-9f84-bda798858b53" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:to="loc_srt_StatementGeographicalAxis_6cdb9778-bbc0-4c00-9f84-bda798858b53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_6cdb9778-bbc0-4c00-9f84-bda798858b53_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_6cdb9778-bbc0-4c00-9f84-bda798858b53" xlink:to="loc_srt_SegmentGeographicalDomain_6cdb9778-bbc0-4c00-9f84-bda798858b53_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_0a38dd71-004a-4a7b-9a39-eab4ffa4c5c9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_6cdb9778-bbc0-4c00-9f84-bda798858b53" xlink:to="loc_srt_SegmentGeographicalDomain_0a38dd71-004a-4a7b-9a39-eab4ffa4c5c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_3fe44177-da8b-4f17-b6dd-142c68c7d613" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0a38dd71-004a-4a7b-9a39-eab4ffa4c5c9" xlink:to="loc_country_US_3fe44177-da8b-4f17-b6dd-142c68c7d613" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_79adda3d-4b12-42a0-b6c4-513d9f518aa8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_0a38dd71-004a-4a7b-9a39-eab4ffa4c5c9" xlink:to="loc_us-gaap_NonUsMember_79adda3d-4b12-42a0-b6c4-513d9f518aa8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_f4483704-05ee-4114-a388-7b1b9a780022" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:to="loc_srt_ConsolidationItemsAxis_f4483704-05ee-4114-a388-7b1b9a780022" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_f4483704-05ee-4114-a388-7b1b9a780022_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_f4483704-05ee-4114-a388-7b1b9a780022" xlink:to="loc_srt_ConsolidationItemsDomain_f4483704-05ee-4114-a388-7b1b9a780022_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_4e8e61e7-25ba-4c41-906b-2eb630fb7a90" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_f4483704-05ee-4114-a388-7b1b9a780022" xlink:to="loc_srt_ConsolidationItemsDomain_4e8e61e7-25ba-4c41-906b-2eb630fb7a90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_faadd421-9074-484e-ae4e-55299548aa15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_4e8e61e7-25ba-4c41-906b-2eb630fb7a90" xlink:to="loc_us-gaap_IntersegmentEliminationMember_faadd421-9074-484e-ae4e-55299548aa15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_c2379f57-4e29-4c12-9446-49b9489f0954" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_4e8e61e7-25ba-4c41-906b-2eb630fb7a90" xlink:to="loc_us-gaap_OperatingSegmentsMember_c2379f57-4e29-4c12-9446-49b9489f0954" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelAxis_a80d6d64-1713-4bbb-a166-56160fd16284" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerSalesChannelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelAxis_a80d6d64-1713-4bbb-a166-56160fd16284" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_a80d6d64-1713-4bbb-a166-56160fd16284_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_a80d6d64-1713-4bbb-a166-56160fd16284" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_a80d6d64-1713-4bbb-a166-56160fd16284_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerSalesChannelDomain_5cdb1084-8e41-4901-8999-6383a54dd767" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerSalesChannelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelAxis_a80d6d64-1713-4bbb-a166-56160fd16284" xlink:to="loc_us-gaap_ContractWithCustomerSalesChannelDomain_5cdb1084-8e41-4901-8999-6383a54dd767" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelDirectlyToConsumerMember_6dbca4dc-8843-45a7-b8f7-688243e8ffea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesChannelDirectlyToConsumerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_5cdb1084-8e41-4901-8999-6383a54dd767" xlink:to="loc_us-gaap_SalesChannelDirectlyToConsumerMember_6dbca4dc-8843-45a7-b8f7-688243e8ffea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesChannelThroughIntermediaryMember_d557db83-890a-4378-8778-bfd96e10bde1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesChannelThroughIntermediaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerSalesChannelDomain_5cdb1084-8e41-4901-8999-6383a54dd767" xlink:to="loc_us-gaap_SalesChannelThroughIntermediaryMember_d557db83-890a-4378-8778-bfd96e10bde1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_1db05c9f-0dd4-4d65-81da-55bbb612d039" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerBasisOfPricingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_147affbc-10c5-4018-a81d-c6e5cbc46b67" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_1db05c9f-0dd4-4d65-81da-55bbb612d039" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_1db05c9f-0dd4-4d65-81da-55bbb612d039_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_1db05c9f-0dd4-4d65-81da-55bbb612d039" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_1db05c9f-0dd4-4d65-81da-55bbb612d039_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_7340bbce-fdfc-4c57-965d-7d2332769788" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_1db05c9f-0dd4-4d65-81da-55bbb612d039" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_7340bbce-fdfc-4c57-965d-7d2332769788" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedPriceContractMember_f64a3302-711d-41d6-95f1-132c64b2f4f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FixedPriceContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_7340bbce-fdfc-4c57-965d-7d2332769788" xlink:to="loc_us-gaap_FixedPriceContractMember_f64a3302-711d-41d6-95f1-132c64b2f4f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimeAndMaterialsContractMember_fc9c3f02-63c6-491a-9c67-7a3ce08f68f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TimeAndMaterialsContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_7340bbce-fdfc-4c57-965d-7d2332769788" xlink:to="loc_us-gaap_TimeAndMaterialsContractMember_fc9c3f02-63c6-491a-9c67-7a3ce08f68f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_65e6532a-a33b-41be-91e2-9b07b7b6ebc5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_adfc54fe-1cc4-4c6b-8624-2818debe7d1a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_65e6532a-a33b-41be-91e2-9b07b7b6ebc5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/PropertyPlantandEquipmentScheduleofPropertyPlantandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_be369806-dfd6-42da-9844-18719b051b8b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0d2848f1-9cdb-431b-b3cf-8998df23cb04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_be369806-dfd6-42da-9844-18719b051b8b" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0d2848f1-9cdb-431b-b3cf-8998df23cb04" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_6fe76376-3520-43fd-9740-b591f28b5ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_0d2848f1-9cdb-431b-b3cf-8998df23cb04" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_6fe76376-3520-43fd-9740-b591f28b5ac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6fe76376-3520-43fd-9740-b591f28b5ac7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_6fe76376-3520-43fd-9740-b591f28b5ac7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6fe76376-3520-43fd-9740-b591f28b5ac7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ea4d9dbe-3fdd-4359-a6d6-f7b727d309d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_6fe76376-3520-43fd-9740-b591f28b5ac7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ea4d9dbe-3fdd-4359-a6d6-f7b727d309d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_5aee131d-23e3-4d06-878a-6df68d11e186" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandBuildingsAndImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ea4d9dbe-3fdd-4359-a6d6-f7b727d309d1" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_5aee131d-23e3-4d06-878a-6df68d11e186" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_b7720da9-7e2b-462e-b3e2-a91cf51a5eb8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ea4d9dbe-3fdd-4359-a6d6-f7b727d309d1" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_b7720da9-7e2b-462e-b3e2-a91cf51a5eb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember_91c29585-7272-49a9-b295-2102e4a4a12d" xlink:href="drs-20250930.xsd#drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_ea4d9dbe-3fdd-4359-a6d6-f7b727d309d1" xlink:to="loc_drs_EquipmentAndOtherCapitalizedPropertyPlantAndEquipmentMember_91c29585-7272-49a9-b295-2102e4a4a12d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_420c0d93-56c0-4c76-8a1d-e068a8ab80c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_be369806-dfd6-42da-9844-18719b051b8b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_420c0d93-56c0-4c76-8a1d-e068a8ab80c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_dbac52d0-77d5-4a9c-b338-a5064ad63a65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_be369806-dfd6-42da-9844-18719b051b8b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_dbac52d0-77d5-4a9c-b338-a5064ad63a65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_939810b0-8d0c-492a-af3e-94f646986e5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_be369806-dfd6-42da-9844-18719b051b8b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_939810b0-8d0c-492a-af3e-94f646986e5d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/IntangibleAssetsScheduleofFiniteLivedIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e498c359-0a60-4662-a293-2feb64bbce46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_57e7cb93-dff0-4773-8979-7548428e9247" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e498c359-0a60-4662-a293-2feb64bbce46" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_57e7cb93-dff0-4773-8979-7548428e9247" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e637e269-a86e-46bc-b7b7-9ae6b44a26a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_57e7cb93-dff0-4773-8979-7548428e9247" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e637e269-a86e-46bc-b7b7-9ae6b44a26a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e637e269-a86e-46bc-b7b7-9ae6b44a26a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e637e269-a86e-46bc-b7b7-9ae6b44a26a4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e637e269-a86e-46bc-b7b7-9ae6b44a26a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a92abc71-cf82-42c4-bdf7-cf89c6b22790" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e637e269-a86e-46bc-b7b7-9ae6b44a26a4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a92abc71-cf82-42c4-bdf7-cf89c6b22790" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AcquiredIntangibleAssetsMember_1b69eec3-ed01-4052-9cc1-e578ed38f25b" xlink:href="drs-20250930.xsd#drs_AcquiredIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a92abc71-cf82-42c4-bdf7-cf89c6b22790" xlink:to="loc_drs_AcquiredIntangibleAssetsMember_1b69eec3-ed01-4052-9cc1-e578ed38f25b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_PatentsAndLicenseMember_b6c5a0a9-ac89-4810-9f5a-c17dc897c061" xlink:href="drs-20250930.xsd#drs_PatentsAndLicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a92abc71-cf82-42c4-bdf7-cf89c6b22790" xlink:to="loc_drs_PatentsAndLicenseMember_b6c5a0a9-ac89-4810-9f5a-c17dc897c061" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_1705d422-a73a-4a8f-80a8-4a4822a39ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e498c359-0a60-4662-a293-2feb64bbce46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_1705d422-a73a-4a8f-80a8-4a4822a39ae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_b671003e-5f8b-4031-87d5-2a0f687bc91a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e498c359-0a60-4662-a293-2feb64bbce46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_b671003e-5f8b-4031-87d5-2a0f687bc91a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3f8edfc-b2c3-4949-9229-450ff85ee9e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e498c359-0a60-4662-a293-2feb64bbce46" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_d3f8edfc-b2c3-4949-9229-450ff85ee9e7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/DebtScheduleofLongTermDebtDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#DebtScheduleofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/DebtScheduleofLongTermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_56b2ee68-1a6f-4c2b-ad4c-bee0a88aa122" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_DebtInstrumentTable_56b2ee68-1a6f-4c2b-ad4c-bee0a88aa122" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_56b2ee68-1a6f-4c2b-ad4c-bee0a88aa122" xlink:to="loc_us-gaap_DebtInstrumentAxis_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6e429f1a-1be7-470b-917a-031494897a21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6454cc2e-6035-4f3b-83b9-98fbfa9e9efe" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6e429f1a-1be7-470b-917a-031494897a21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementTermLoanAMember_9ce11e21-9294-4ed6-8d2e-7e2fc28ed3ba" xlink:href="drs-20250930.xsd#drs_A2022CreditAgreementTermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6e429f1a-1be7-470b-917a-031494897a21" xlink:to="loc_drs_A2022CreditAgreementTermLoanAMember_9ce11e21-9294-4ed6-8d2e-7e2fc28ed3ba" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_5fe6720e-aa27-498f-89de-7373f7aab33f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_56b2ee68-1a6f-4c2b-ad4c-bee0a88aa122" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_5fe6720e-aa27-498f-89de-7373f7aab33f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5fe6720e-aa27-498f-89de-7373f7aab33f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5fe6720e-aa27-498f-89de-7373f7aab33f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5fe6720e-aa27-498f-89de-7373f7aab33f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b275966f-60c2-47a0-aea0-36f172be7e64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5fe6720e-aa27-498f-89de-7373f7aab33f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b275966f-60c2-47a0-aea0-36f172be7e64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_bf3b386e-2b82-4388-b091-677935998508" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_b275966f-60c2-47a0-aea0-36f172be7e64" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_bf3b386e-2b82-4388-b091-677935998508" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_895f87f6-5a28-44d9-a018-5bd9866b0133" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_895f87f6-5a28-44d9-a018-5bd9866b0133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_FinanceLeaseLiabilityAndOtherLiability_53cffc75-6bbc-451b-aa52-5b3c8cbe73b9" xlink:href="drs-20250930.xsd#drs_FinanceLeaseLiabilityAndOtherLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_drs_FinanceLeaseLiabilityAndOtherLiability_53cffc75-6bbc-451b-aa52-5b3c8cbe73b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_cb7b1be4-60ab-4f96-ba7c-eb933f3f7c32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_ShortTermBorrowings_cb7b1be4-60ab-4f96-ba7c-eb933f3f7c32" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_DebtAndCapitalLeaseObligationsGross_6d1d0d4b-d3ab-40e0-858a-ccbff52022b5" xlink:href="drs-20250930.xsd#drs_DebtAndCapitalLeaseObligationsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_drs_DebtAndCapitalLeaseObligationsGross_6d1d0d4b-d3ab-40e0-858a-ccbff52022b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3247d99b-7621-41fe-8710-09dd57a0d7f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3247d99b-7621-41fe-8710-09dd57a0d7f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtAndCapitalLeaseObligations_aba0f594-2438-4450-83e7-910807a7455a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_DebtAndCapitalLeaseObligations_aba0f594-2438-4450-83e7-910807a7455a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_34bc080d-eb4c-4c8c-b9ea-44da57abd312" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_DebtCurrent_34bc080d-eb4c-4c8c-b9ea-44da57abd312" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_5fb59cba-ce71-4680-ad49-ba8a976636f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_02237cbc-ed06-42fa-b05e-7f52e3cc9c69" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_5fb59cba-ce71-4680-ad49-ba8a976636f4" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_4e0bcfef-b832-498e-ae5a-7baf5945ce76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_DebtInstrumentTable_4e0bcfef-b832-498e-ae5a-7baf5945ce76" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_bcc42673-ec91-413a-8e3e-a6d02af84c0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4e0bcfef-b832-498e-ae5a-7baf5945ce76" xlink:to="loc_us-gaap_DebtInstrumentAxis_bcc42673-ec91-413a-8e3e-a6d02af84c0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bcc42673-ec91-413a-8e3e-a6d02af84c0c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_bcc42673-ec91-413a-8e3e-a6d02af84c0c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bcc42673-ec91-413a-8e3e-a6d02af84c0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_51b49e1b-ee46-45c5-bced-12cbd1c5ac2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_bcc42673-ec91-413a-8e3e-a6d02af84c0c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_51b49e1b-ee46-45c5-bced-12cbd1c5ac2d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementMember_4b186a0d-8370-4ed6-8b32-3416c9b3fac5" xlink:href="drs-20250930.xsd#drs_A2022CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_51b49e1b-ee46-45c5-bced-12cbd1c5ac2d" xlink:to="loc_drs_A2022CreditAgreementMember_4b186a0d-8370-4ed6-8b32-3416c9b3fac5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_A2022CreditAgreementTermLoanAMember_3ad4b931-b2e0-4159-be7f-6faeacf4780a" xlink:href="drs-20250930.xsd#drs_A2022CreditAgreementTermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_drs_A2022CreditAgreementMember_4b186a0d-8370-4ed6-8b32-3416c9b3fac5" xlink:to="loc_drs_A2022CreditAgreementTermLoanAMember_3ad4b931-b2e0-4159-be7f-6faeacf4780a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_2d934b7e-76d5-4e31-944e-92cb6b8dbb86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_drs_A2022CreditAgreementMember_4b186a0d-8370-4ed6-8b32-3416c9b3fac5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_2d934b7e-76d5-4e31-944e-92cb6b8dbb86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_FinancialInstitutionCreditFacilitiesMember_de3dc43b-4b68-4dbe-ba12-d081e36d7d4b" xlink:href="drs-20250930.xsd#drs_FinancialInstitutionCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_51b49e1b-ee46-45c5-bced-12cbd1c5ac2d" xlink:to="loc_drs_FinancialInstitutionCreditFacilitiesMember_de3dc43b-4b68-4dbe-ba12-d081e36d7d4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4e0bcfef-b832-498e-ae5a-7baf5945ce76" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2aac1eb7-db5b-4fec-9bca-7829641f9f19" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_b3e1e94f-8ea8-42a4-9693-e35f83d1a7f9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2aac1eb7-db5b-4fec-9bca-7829641f9f19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableOtherPayablesMember_1dd10881-8e1b-466c-821f-35298e5bac50" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesPayableOtherPayablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2aac1eb7-db5b-4fec-9bca-7829641f9f19" xlink:to="loc_us-gaap_NotesPayableOtherPayablesMember_1dd10881-8e1b-466c-821f-35298e5bac50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_2d129e18-aaf9-4e71-ac54-08d9c9f534f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2aac1eb7-db5b-4fec-9bca-7829641f9f19" xlink:to="loc_us-gaap_LineOfCreditMember_2d129e18-aaf9-4e71-ac54-08d9c9f534f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_2f48883f-aca6-41f6-a8ea-3171d0eb6430" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_4e0bcfef-b832-498e-ae5a-7baf5945ce76" xlink:to="loc_srt_RangeAxis_2f48883f-aca6-41f6-a8ea-3171d0eb6430" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_2f48883f-aca6-41f6-a8ea-3171d0eb6430_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_2f48883f-aca6-41f6-a8ea-3171d0eb6430" xlink:to="loc_srt_RangeMember_2f48883f-aca6-41f6-a8ea-3171d0eb6430_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_cea142a9-4a43-4773-9770-b0a251453705" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_2f48883f-aca6-41f6-a8ea-3171d0eb6430" xlink:to="loc_srt_RangeMember_cea142a9-4a43-4773-9770-b0a251453705" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_6d154bc4-1c93-4fbf-bb34-d712f128c666" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_cea142a9-4a43-4773-9770-b0a251453705" xlink:to="loc_srt_MinimumMember_6d154bc4-1c93-4fbf-bb34-d712f128c666" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_792c0d18-9710-489a-8a9b-3d5ac3b8b5fa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_cea142a9-4a43-4773-9770-b0a251453705" xlink:to="loc_srt_MaximumMember_792c0d18-9710-489a-8a9b-3d5ac3b8b5fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35429fac-7a3e-4455-8875-56b5606c0c31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35429fac-7a3e-4455-8875-56b5606c0c31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_42e8dfe5-6ae0-49c9-bf38-3f555d7b7307" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_42e8dfe5-6ae0-49c9-bf38-3f555d7b7307" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_79f50e6f-707c-4aa2-8426-1d4c74fb3720" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_79f50e6f-707c-4aa2-8426-1d4c74fb3720" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_c6bce996-1cad-4a81-b889-9e54f166d8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_c6bce996-1cad-4a81-b889-9e54f166d8f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_ee6a0c7b-a0d8-47fa-a510-b255fb80d3cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_LongTermDebtFairValue_ee6a0c7b-a0d8-47fa-a510-b255fb80d3cf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f249d428-f853-48c1-bc2c-bcf2e7d73067" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f249d428-f853-48c1-bc2c-bcf2e7d73067" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_4ab766fb-2bcc-44b5-b525-b65141be0cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_LineOfCredit_4ab766fb-2bcc-44b5-b525-b65141be0cf9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_52780904-2fac-4d37-a92d-00c1ab09faf2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0f7e5c02-8ee2-4868-a44b-2031c9b48de8" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_52780904-2fac-4d37-a92d-00c1ab09faf2" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/DerivativeInstrumentsScheduleofDerivativeInstrumentsinStatementofFinancialPositionDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#DerivativeInstrumentsScheduleofDerivativeInstrumentsinStatementofFinancialPositionDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/DerivativeInstrumentsScheduleofDerivativeInstrumentsinStatementofFinancialPositionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9219bccc-62fe-49c1-ba61-c053f8c46099" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed259471-ee70-44db-8c4b-ac7a329153ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9219bccc-62fe-49c1-ba61-c053f8c46099" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed259471-ee70-44db-8c4b-ac7a329153ed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_3422cdee-ef8a-4c5e-a651-a7ce06cbce14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ed259471-ee70-44db-8c4b-ac7a329153ed" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_3422cdee-ef8a-4c5e-a651-a7ce06cbce14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3422cdee-ef8a-4c5e-a651-a7ce06cbce14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3422cdee-ef8a-4c5e-a651-a7ce06cbce14" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3422cdee-ef8a-4c5e-a651-a7ce06cbce14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_314d2291-cc11-4b3c-bce0-ca35ee3aad28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3422cdee-ef8a-4c5e-a651-a7ce06cbce14" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_314d2291-cc11-4b3c-bce0-ca35ee3aad28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_97e0a1f1-924f-4fac-b949-a2e6191d9708" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_314d2291-cc11-4b3c-bce0-ca35ee3aad28" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_97e0a1f1-924f-4fac-b949-a2e6191d9708" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_857e3a5e-92c4-4ee5-9412-758fe47a2d7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9219bccc-62fe-49c1-ba61-c053f8c46099" xlink:to="loc_us-gaap_DerivativeNotionalAmount_857e3a5e-92c4-4ee5-9412-758fe47a2d7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeNet_4847c054-276f-4cc7-a314-37f392f05750" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_9219bccc-62fe-49c1-ba61-c053f8c46099" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeNet_4847c054-276f-4cc7-a314-37f392f05750" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/EarningsPerShareEPSShareRepurchasesandDividendsNarrativeDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#EarningsPerShareEPSShareRepurchasesandDividendsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/EarningsPerShareEPSShareRepurchasesandDividendsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramLineItems_5523ade5-caba-4028-a360-e97a388c553b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramTable_b389a6c2-17a8-41c8-a355-7a84e91b95fd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ShareRepurchaseProgramTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_5523ade5-caba-4028-a360-e97a388c553b" xlink:to="loc_srt_ShareRepurchaseProgramTable_b389a6c2-17a8-41c8-a355-7a84e91b95fd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_4cfba503-7647-4235-a29b-4c3f49b166f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ShareRepurchaseProgramTable_b389a6c2-17a8-41c8-a355-7a84e91b95fd" xlink:to="loc_us-gaap_StatementClassOfStockAxis_4cfba503-7647-4235-a29b-4c3f49b166f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_4cfba503-7647-4235-a29b-4c3f49b166f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4cfba503-7647-4235-a29b-4c3f49b166f1" xlink:to="loc_us-gaap_ClassOfStockDomain_4cfba503-7647-4235-a29b-4c3f49b166f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_0bf429a7-f291-4dc5-a01d-7e252621174d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_4cfba503-7647-4235-a29b-4c3f49b166f1" xlink:to="loc_us-gaap_ClassOfStockDomain_0bf429a7-f291-4dc5-a01d-7e252621174d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_2161149a-6f7f-443e-bb94-4349e0d7daf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_0bf429a7-f291-4dc5-a01d-7e252621174d" xlink:to="loc_us-gaap_CommonClassAMember_2161149a-6f7f-443e-bb94-4349e0d7daf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_d9306dd2-a512-4212-aa39-cc0b419548a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ShareRepurchaseProgramTable_b389a6c2-17a8-41c8-a355-7a84e91b95fd" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_d9306dd2-a512-4212-aa39-cc0b419548a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_d9306dd2-a512-4212-aa39-cc0b419548a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_d9306dd2-a512-4212-aa39-cc0b419548a8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_d9306dd2-a512-4212-aa39-cc0b419548a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_d5e096a3-75fa-4f8c-908f-0da5ebaa990e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_d9306dd2-a512-4212-aa39-cc0b419548a8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_d5e096a3-75fa-4f8c-908f-0da5ebaa990e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_f16bc534-6210-4296-a3ee-48597976436f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_d5e096a3-75fa-4f8c-908f-0da5ebaa990e" xlink:to="loc_us-gaap_SubsequentEventMember_f16bc534-6210-4296-a3ee-48597976436f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_7ce076cc-d5d3-4cc0-807c-4cd7996df4cf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_5523ade5-caba-4028-a360-e97a388c553b" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_7ce076cc-d5d3-4cc0-807c-4cd7996df4cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_735a218a-94e0-4370-96cd-9045decf595a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_5523ade5-caba-4028-a360-e97a388c553b" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_735a218a-94e0-4370-96cd-9045decf595a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_9626363a-8dc5-45dd-b467-94458c4c606f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramLineItems_5523ade5-caba-4028-a360-e97a388c553b" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_9626363a-8dc5-45dd-b467-94458c4c606f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyLiabilityLineItems_e2fd717f-91d9-4ddf-98b8-2363515879d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductWarrantyLiabilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductWarrantyLiabilityTable_cdaef8ac-aab6-4899-8e6d-9b1de0a35300" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductWarrantyLiabilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_e2fd717f-91d9-4ddf-98b8-2363515879d3" xlink:to="loc_us-gaap_ProductWarrantyLiabilityTable_cdaef8ac-aab6-4899-8e6d-9b1de0a35300" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_3241ace9-3de7-4696-8fd4-6d7ac56c92bc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ProductWarrantyLiabilityTable_cdaef8ac-aab6-4899-8e6d-9b1de0a35300" xlink:to="loc_srt_RangeAxis_3241ace9-3de7-4696-8fd4-6d7ac56c92bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3241ace9-3de7-4696-8fd4-6d7ac56c92bc_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_3241ace9-3de7-4696-8fd4-6d7ac56c92bc" xlink:to="loc_srt_RangeMember_3241ace9-3de7-4696-8fd4-6d7ac56c92bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e4906f33-90bd-4227-869c-2961a366ef6a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_3241ace9-3de7-4696-8fd4-6d7ac56c92bc" xlink:to="loc_srt_RangeMember_e4906f33-90bd-4227-869c-2961a366ef6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ef61eed4-aded-46aa-837f-69f6059323ae" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_e4906f33-90bd-4227-869c-2961a366ef6a" xlink:to="loc_srt_MinimumMember_ef61eed4-aded-46aa-837f-69f6059323ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_fb6513fd-4a07-440b-a00d-db3b44c51f22" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_e4906f33-90bd-4227-869c-2961a366ef6a" xlink:to="loc_srt_MaximumMember_fb6513fd-4a07-440b-a00d-db3b44c51f22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_StandardProductWarrantyTerm_322b4524-647b-498c-af70-aa2422d8137e" xlink:href="drs-20250930.xsd#drs_StandardProductWarrantyTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductWarrantyLiabilityLineItems_e2fd717f-91d9-4ddf-98b8-2363515879d3" xlink:to="loc_drs_StandardProductWarrantyTerm_322b4524-647b-498c-af70-aa2422d8137e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/RelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_bf6ea54c-9f17-4099-8643-56b1aadfc20d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_bf6ea54c-9f17-4099-8643-56b1aadfc20d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_bf6ea54c-9f17-4099-8643-56b1aadfc20d" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5" xlink:to="loc_us-gaap_RelatedPartyDomain_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_29a1b0d1-087e-4902-9b22-a5b096f4eb16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_fd1371a3-61b1-408a-9701-9fe3bdc4e8b5" xlink:to="loc_us-gaap_RelatedPartyDomain_29a1b0d1-087e-4902-9b22-a5b096f4eb16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_216008a2-ca16-4d20-add7-5a10bc72208b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_29a1b0d1-087e-4902-9b22-a5b096f4eb16" xlink:to="loc_us-gaap_RelatedPartyMember_216008a2-ca16-4d20-add7-5a10bc72208b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_bf6ea54c-9f17-4099-8643-56b1aadfc20d" xlink:to="loc_srt_CounterpartyNameAxis_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_91aaafae-eb07-46e4-a5c0-cec27328b66e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_1ffd6d19-4a1b-478b-a3c7-43b0ec7e8655" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_91aaafae-eb07-46e4-a5c0-cec27328b66e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_LeonardoSpAMember_5e4b4d18-d796-4198-9335-ce506c659f3f" xlink:href="drs-20250930.xsd#drs_LeonardoSpAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_91aaafae-eb07-46e4-a5c0-cec27328b66e" xlink:to="loc_drs_LeonardoSpAMember_5e4b4d18-d796-4198-9335-ce506c659f3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_UnnamedPrivateCompanyMember_b9514185-0462-4ef2-95e9-60024ef0633f" xlink:href="drs-20250930.xsd#drs_UnnamedPrivateCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_91aaafae-eb07-46e4-a5c0-cec27328b66e" xlink:to="loc_drs_UnnamedPrivateCompanyMember_b9514185-0462-4ef2-95e9-60024ef0633f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_91513363-000e-4feb-bc02-344a913b20fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_91513363-000e-4feb-bc02-344a913b20fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_15df7906-bdf3-4d4e-9654-0d1f16dfe0f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_CostOfRevenue_15df7906-bdf3-4d4e-9654-0d1f16dfe0f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_af35712e-77f5-4f7a-ba71-2e415644f137" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_af35712e-77f5-4f7a-ba71-2e415644f137" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_5f166472-aa1d-4ae3-9141-73f2f738262e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_AccountsPayableCurrent_5f166472-aa1d-4ae3-9141-73f2f738262e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_49093579-c30d-4bcf-9ebf-9fa0e8d9c8db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_49093579-c30d-4bcf-9ebf-9fa0e8d9c8db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Investments_2cb23027-4311-4411-a9c0-3764cad78f00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Investments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_us-gaap_Investments_2cb23027-4311-4411-a9c0-3764cad78f00" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_NumberOfBoardSeats_f8d881fe-08d0-444e-afcc-a88045dfef96" xlink:href="drs-20250930.xsd#drs_NumberOfBoardSeats"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6e812927-f257-46e6-ae43-e1e44ed87669" xlink:to="loc_drs_NumberOfBoardSeats_f8d881fe-08d0-444e-afcc-a88045dfef96" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#SegmentInformationRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationRevenuesExpensesandOperatingEarningsbySegmentandReconciliationtoEarningsbeforeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_733d4808-5849-4283-9048-039cfb26f0a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_733d4808-5849-4283-9048-039cfb26f0a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_4600d7a1-a191-4cfc-a29b-0c0e2ea12578" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_733d4808-5849-4283-9048-039cfb26f0a6" xlink:to="loc_srt_ConsolidationItemsAxis_4600d7a1-a191-4cfc-a29b-0c0e2ea12578" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_4600d7a1-a191-4cfc-a29b-0c0e2ea12578_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_4600d7a1-a191-4cfc-a29b-0c0e2ea12578" xlink:to="loc_srt_ConsolidationItemsDomain_4600d7a1-a191-4cfc-a29b-0c0e2ea12578_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_74bff216-0948-437a-9b72-eba2769065d1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_4600d7a1-a191-4cfc-a29b-0c0e2ea12578" xlink:to="loc_srt_ConsolidationItemsDomain_74bff216-0948-437a-9b72-eba2769065d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_8a038489-95d6-49cc-9d4c-d7680906f914" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_74bff216-0948-437a-9b72-eba2769065d1" xlink:to="loc_us-gaap_OperatingSegmentsMember_8a038489-95d6-49cc-9d4c-d7680906f914" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_CorporateAndEliminationsMember_2a3f465c-d120-4072-9b26-6e7e78afc6bf" xlink:href="drs-20250930.xsd#drs_CorporateAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_74bff216-0948-437a-9b72-eba2769065d1" xlink:to="loc_drs_CorporateAndEliminationsMember_2a3f465c-d120-4072-9b26-6e7e78afc6bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_2628b91d-5850-41eb-a0d9-af67da45417e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_733d4808-5849-4283-9048-039cfb26f0a6" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_2628b91d-5850-41eb-a0d9-af67da45417e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_2628b91d-5850-41eb-a0d9-af67da45417e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_2628b91d-5850-41eb-a0d9-af67da45417e" xlink:to="loc_us-gaap_SegmentDomain_2628b91d-5850-41eb-a0d9-af67da45417e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_47707d07-7ab8-4ea5-8f10-5a1757958ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_2628b91d-5850-41eb-a0d9-af67da45417e" xlink:to="loc_us-gaap_SegmentDomain_47707d07-7ab8-4ea5-8f10-5a1757958ba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_57c9d619-a835-4844-8126-10489b9f5b9f" xlink:href="drs-20250930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_47707d07-7ab8-4ea5-8f10-5a1757958ba4" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_57c9d619-a835-4844-8126-10489b9f5b9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_0ffbccac-b6a4-4338-84e3-2691749acca0" xlink:href="drs-20250930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_47707d07-7ab8-4ea5-8f10-5a1757958ba4" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_0ffbccac-b6a4-4338-84e3-2691749acca0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_caa70a0c-54c5-489d-ac4a-e51bc8779205" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_caa70a0c-54c5-489d-ac4a-e51bc8779205" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_4d2154b3-0b9e-43e2-8808-ab9e03014c64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_CostOfRevenue_4d2154b3-0b9e-43e2-8808-ab9e03014c64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralAndAdministrativeExpense_65e46921-c384-4745-8fa4-2b5fd91484f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_OtherGeneralAndAdministrativeExpense_65e46921-c384-4745-8fa4-2b5fd91484f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_9938e107-75bb-4391-8666-572c5f50966c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_9938e107-75bb-4391-8666-572c5f50966c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_d321a9c5-1ec3-486b-92a2-87858c99ecc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_d321a9c5-1ec3-486b-92a2-87858c99ecc3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_b0ad5915-5841-42ba-864d-a844c122047c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_b0ad5915-5841-42ba-864d-a844c122047c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_18076bda-3132-4824-8564-e3222c465598" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_OperatingIncomeLoss_18076bda-3132-4824-8564-e3222c465598" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_68afcc71-567c-4a9c-8d3f-e6272a62e291" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_68afcc71-567c-4a9c-8d3f-e6272a62e291" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_39266775-5fc5-4fd3-8e07-ba73043be528" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_39266775-5fc5-4fd3-8e07-ba73043be528" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_2906d438-3242-4219-bcd8-92ba1c9b29d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3da67a1e-333b-4b40-9d1d-5d80c7d829ec" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_2906d438-3242-4219-bcd8-92ba1c9b29d7" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationRevenuesandIntersegmentRevenuesDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#SegmentInformationRevenuesandIntersegmentRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationRevenuesandIntersegmentRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_fb92b586-2724-46eb-8a88-06f0fa9aa629" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e2aaf304-2f88-4219-a0af-abbf96700bed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_fb92b586-2724-46eb-8a88-06f0fa9aa629" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e2aaf304-2f88-4219-a0af-abbf96700bed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_ede07141-f2ce-427f-90f5-ce78079a5fe3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e2aaf304-2f88-4219-a0af-abbf96700bed" xlink:to="loc_srt_ConsolidationItemsAxis_ede07141-f2ce-427f-90f5-ce78079a5fe3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_ede07141-f2ce-427f-90f5-ce78079a5fe3_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_ede07141-f2ce-427f-90f5-ce78079a5fe3" xlink:to="loc_srt_ConsolidationItemsDomain_ede07141-f2ce-427f-90f5-ce78079a5fe3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_37d2feee-9466-487b-90c4-dedb6e077e1c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_ede07141-f2ce-427f-90f5-ce78079a5fe3" xlink:to="loc_srt_ConsolidationItemsDomain_37d2feee-9466-487b-90c4-dedb6e077e1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_28066b4e-6055-43e9-acc9-3ca4d556cfe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_37d2feee-9466-487b-90c4-dedb6e077e1c" xlink:to="loc_us-gaap_IntersegmentEliminationMember_28066b4e-6055-43e9-acc9-3ca4d556cfe4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_e5385320-9477-40db-9288-73f3c3afe18d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_e2aaf304-2f88-4219-a0af-abbf96700bed" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_e5385320-9477-40db-9288-73f3c3afe18d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_e5385320-9477-40db-9288-73f3c3afe18d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_e5385320-9477-40db-9288-73f3c3afe18d" xlink:to="loc_us-gaap_SegmentDomain_e5385320-9477-40db-9288-73f3c3afe18d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_6dbc07b0-9dc5-4a4b-a529-c5dbf1f61593" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_e5385320-9477-40db-9288-73f3c3afe18d" xlink:to="loc_us-gaap_SegmentDomain_6dbc07b0-9dc5-4a4b-a529-c5dbf1f61593" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_bff18aad-f4e7-4600-8630-830f8f447b85" xlink:href="drs-20250930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6dbc07b0-9dc5-4a4b-a529-c5dbf1f61593" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_bff18aad-f4e7-4600-8630-830f8f447b85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_e2766c85-e0ca-461e-9d51-b888d9eaab71" xlink:href="drs-20250930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6dbc07b0-9dc5-4a4b-a529-c5dbf1f61593" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_e2766c85-e0ca-461e-9d51-b888d9eaab71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_9a116ceb-b32e-43c5-9828-038030475bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_fb92b586-2724-46eb-8a88-06f0fa9aa629" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_9a116ceb-b32e-43c5-9828-038030475bb9" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationDepreciationbySegmentDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#SegmentInformationDepreciationbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationDepreciationbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_504a33f2-2941-4b69-8d1d-021ec3c369fe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8b25ffb6-794d-488c-8017-13887f7672e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_504a33f2-2941-4b69-8d1d-021ec3c369fe" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8b25ffb6-794d-488c-8017-13887f7672e2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_9075641a-c771-4ebe-8bbf-316a8037bd7f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8b25ffb6-794d-488c-8017-13887f7672e2" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_9075641a-c771-4ebe-8bbf-316a8037bd7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9075641a-c771-4ebe-8bbf-316a8037bd7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9075641a-c771-4ebe-8bbf-316a8037bd7f" xlink:to="loc_us-gaap_SegmentDomain_9075641a-c771-4ebe-8bbf-316a8037bd7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_e24e19a5-2f28-4340-b0cf-609bafb00ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_9075641a-c771-4ebe-8bbf-316a8037bd7f" xlink:to="loc_us-gaap_SegmentDomain_e24e19a5-2f28-4340-b0cf-609bafb00ed6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_a44b9ba8-539d-4a50-ad1b-ff09363bde46" xlink:href="drs-20250930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e24e19a5-2f28-4340-b0cf-609bafb00ed6" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_a44b9ba8-539d-4a50-ad1b-ff09363bde46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_46addb5a-a8ef-4b39-a148-c052c0f2733c" xlink:href="drs-20250930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e24e19a5-2f28-4340-b0cf-609bafb00ed6" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_46addb5a-a8ef-4b39-a148-c052c0f2733c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_1e9ff5fc-7651-4d99-b096-f478303efa92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_504a33f2-2941-4b69-8d1d-021ec3c369fe" xlink:to="loc_us-gaap_Depreciation_1e9ff5fc-7651-4d99-b096-f478303efa92" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.leonardodrs.com/role/SegmentInformationTotalAssetsbySegmentDetails" xlink:type="simple" xlink:href="drs-20250930.xsd#SegmentInformationTotalAssetsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.leonardodrs.com/role/SegmentInformationTotalAssetsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_ae278f15-cf02-4243-a514-47978d87d613" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_ae41445c-6b4e-4391-a4fb-4833281c8dc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_ae278f15-cf02-4243-a514-47978d87d613" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_ae41445c-6b4e-4391-a4fb-4833281c8dc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_ac423df1-6d95-41c5-8d26-3133c4d0efda" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_ae41445c-6b4e-4391-a4fb-4833281c8dc8" xlink:to="loc_srt_ConsolidationItemsAxis_ac423df1-6d95-41c5-8d26-3133c4d0efda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_ac423df1-6d95-41c5-8d26-3133c4d0efda_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_ac423df1-6d95-41c5-8d26-3133c4d0efda" xlink:to="loc_srt_ConsolidationItemsDomain_ac423df1-6d95-41c5-8d26-3133c4d0efda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_1e892243-56d7-4427-9186-cb3e1eb82d01" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_ac423df1-6d95-41c5-8d26-3133c4d0efda" xlink:to="loc_srt_ConsolidationItemsDomain_1e892243-56d7-4427-9186-cb3e1eb82d01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_a61be993-05ef-4297-a54f-e13b71be0417" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1e892243-56d7-4427-9186-cb3e1eb82d01" xlink:to="loc_us-gaap_OperatingSegmentsMember_a61be993-05ef-4297-a54f-e13b71be0417" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_CorporateAndEliminationsMember_d4f7ee8f-375a-4bbe-a218-c00fa8c6d731" xlink:href="drs-20250930.xsd#drs_CorporateAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1e892243-56d7-4427-9186-cb3e1eb82d01" xlink:to="loc_drs_CorporateAndEliminationsMember_d4f7ee8f-375a-4bbe-a218-c00fa8c6d731" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_d926a286-9149-4a23-adc3-7310e4ddd124" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_ae41445c-6b4e-4391-a4fb-4833281c8dc8" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_d926a286-9149-4a23-adc3-7310e4ddd124" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_d926a286-9149-4a23-adc3-7310e4ddd124_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_d926a286-9149-4a23-adc3-7310e4ddd124" xlink:to="loc_us-gaap_SegmentDomain_d926a286-9149-4a23-adc3-7310e4ddd124_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_eb88581c-804a-4bd9-977e-0699210761f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_d926a286-9149-4a23-adc3-7310e4ddd124" xlink:to="loc_us-gaap_SegmentDomain_eb88581c-804a-4bd9-977e-0699210761f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_AdvancedSensingAndComputingSegmentMember_22a08439-b508-4464-b4f4-3abaff1acd7b" xlink:href="drs-20250930.xsd#drs_AdvancedSensingAndComputingSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_eb88581c-804a-4bd9-977e-0699210761f1" xlink:to="loc_drs_AdvancedSensingAndComputingSegmentMember_22a08439-b508-4464-b4f4-3abaff1acd7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_drs_IntegratedMissionSystemsSegmentMember_13c21ec3-985c-49d7-9c92-2ec649cb98bb" xlink:href="drs-20250930.xsd#drs_IntegratedMissionSystemsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_eb88581c-804a-4bd9-977e-0699210761f1" xlink:to="loc_drs_IntegratedMissionSystemsSegmentMember_13c21ec3-985c-49d7-9c92-2ec649cb98bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_c7766df3-7b16-4153-a4ed-4129a18e8f5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_ae278f15-cf02-4243-a514-47978d87d613" xlink:to="loc_us-gaap_Assets_c7766df3-7b16-4153-a4ed-4129a18e8f5b" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
